The invention relates to a backflow preventing check valve with a housing in which a closing member is arranged, movable between a closing position and an opening position, and abutting with a sealing region on a valve seat in the closed position. A device is provided for pressure compensation when the backflow preventer is closed and a fluid volume is occluded on the outflow side.
Check valves are used in gas, water or the like supply lines in order to prevent a backflow of the fluid against the regular throughflow direction. Thus check valves are also increasingly being built into water lines, in order to counter the penetration of dirty water into the fresh water supply line in the case of a reduced pressure.
However, the use of such check valves in the field of single lever mixing fittings frequently gives rise to the problem that the water, which is trapped between the closed check valve on the one hand and the likewise closed valve seat on the other hand when the cold water side or hot water side is shut off, is strongly heated up by external influences until system pressures arise which lead to damage to the weakest portion of the supply line and thus frequently to the check valve. This can ultimately result in a closure of the supply line or to a likewise undesired crossflow.
A check valve of the kind mentioned at the beginning has therefore even already been provided, the housing of which has a partial region on the inflow side formed as a bellows and supported against the throughflow direction by an annular flange provided in the pipe line (cf. DE 196 50 031 A1); when an internal pressure increase builds up between the single lever mixing fitting and the check valve, the housing can thus be axially compressed in its partial region formed as a bellows, such that pressure relief occurs. In order to be able to attain a sufficient pressure relief, however, the housing has to have a comparatively large cross section and/or a long compressible partial region.
A check valve has therefore already been made which carries on the end of its closing member a hood-shaped extension with a lateral outlet opening (see WO 93/01 435). The bypass channel leading to the outlet opening of the extension, which serves as an excess pressure valve, is closed by means of a valve closure element which is lifted when the internal pressure rises, and releases the outlet opening for the fluid flowing back through the bypass channel. However, it is disadvantageous that with this check valve a partial quantity of the fluid can flow back through the closing member to the inflow side of the check valve.
The object therefore exists in particular of providing a backflow preventer of the kind mentioned at the beginning which is distinguished by a constant, usual constructional length and which reliably prevents a backflow of the fluid. The backflow preventer is also to effectively counter an excessive internal pressure increase.
The attainment of this object according to the invention particularly is provided in that, in the backflow preventer of the kind mentioned at the beginning, at least one pressure compensation space is connected to the space bounded by the closing member on the outflow side in the closing position, which has a receiving volume corresponds approximately to the volume extent of the enclosed fluid, and is situated outside the space bounded on the outflow side.
The backflow preventer according to the invention has a pressure compensation space which is situated outside the space bounded on the outflow side. The space on the outflow side, bounded by the closing member in the closing position, is connected to a pressure compensation space. When the internal pressure increases, a partial quantity of the expanding fluid can temporarily escape into the pressure compensation space. Since the pressure compensation space is corresponds approximately to the volume extent of the enclosed fluid, a sufficient pressure relief is possible in order to prevent continuing damage due to pressure, perhaps to the backflow preventer.
A preferred embodiment according to the invention provides here that the pressure compensation space has as partitions a coating at least locally covering the closing member on the inflow side, together with the coated region of the closing member, and that the closing member has a passage channel between the outflow side and the pressure compensation space. In this embodiment, the closing member carries a coating which encloses the pressure compensation space between itself and the coated region of the closing member. A passage channel opens into this pressure compensation space, and is provided between the outflow side of the closing member and the pressure compensation space. When the internal pressure rises, a partial quantity of the fluid can get through the passage channel into the pressure compensation space, where it expands the coating of the closing member in the form of a bubble.
It is advantageous here if the pressure compensation space is about cushion-shaped and arranged on the inflow side of the closing member and preferably connected to this and, via a passage channel, connected to the outflow side.
A development of the invention of importance meriting its own protection provides that the cushion-shaped pressure compensation space extends over the side of the closing member facing the inflow side and preferably over its lateral sealing region, and forms in this sealing region a sealing inlay passing around between the closing member and a valve seat on the housing. The cushion-shaped pressure compensation space, preferably formed by a coating of the closing member, extends over the lateral sealing region of the closing member and forms there a sealing inlay passing around between the closing member on the one hand and the opposed valve seat on the other hand. When the internal pressure rises, not only does a pressure relief occur, but also the closing member with this sealing inlay is also increasingly pressed against the valve seat, so that the check valve is also capable of withstanding high pressures.
Another embodiment according to the invention provides that the pressure compensation space is formed as an annular sleeve locally covering at least the inside of the inflow side housing section and connected to the outflow side by a passage channel. In this embodiment, an annular sleeve is provided which locally covers the inner side of the inflow-side housing section. The annular sleeve encloses between itself and the housing inner wall a pressure compensation space which is connected by a passage channel to the outflow side of the backflow preventer.
Also in this embodiment, the annular sleeve can extend as far as over the region of the valve seat and thereby form there a sealing inlay passing around between the closing member and the valve seat on the housing.
An embodiment according to the invention which can be produced from few parts provides that the annular sleeve extends out as far as over an outer sealing region and forms there an outer ring seal, at which the annular seal preferably has an annular bead.
It is particularly advantageous if the wall of the pressure compensation space is formed of silicone or the like elastic material. If the coating of the closing member, the annular sleeve or the like wall of the pressure compensation space is formed of silicone or another elastic material, this wall can expand in the form of a bubble when the internal pressure rises.
A development according to the invention of importance meriting its own protection provides that the passage opening leading to the passage channel or the like to the pressure compensation space is tightly closed by a closure piece and that the closure piece is formed as a predetermined breaking place, has a predetermined breaking place, and/or is bordered by a predetermined breaking place, which opens the passage channel or the passage opening when a defined fluid pressure is exceeded on the inflow side of the closing member. In this developed embodiment, the passage opening leading to the pressure compensation space is tightly closed by a closure piece. If the fluid pressure on the outflow side of the closing member exceeds a defined limiting value, the passage opening is opened at the predetermined breaking places in the region of the closing member. Thus the closure piece protects the pressure compensation space up to a defined pressure value, so that this pressure compensation space remains unloaded as long as the fluid pressure on the outflow side of the closing member does not exceed the defined limiting value.
Here it is particularly advantageous if the closure piece is formed as a weakening of the material of the closing member or of the housing in the region of the passage channel or the like passage opening.